A camera with a single small lens that cannot be adjusted to focus on objects at different distances.
In order to have most objects appear in focus, a fixed-focus lens must be very small and have a tiny aperture (opening to the sensor). This allows objects at a wide range of distances to appear in focus.
The small lens and aperture limits the amount of light that reaches the sensor, however, which limits photo quality. Auto-focus lenses often allow much better photo quality.
There is no maximum focus distance for a fixed-focus lens, only a minimum. In other words, objects at 20 feet away will appear equally in focus as objects 2 miles away, but an object 1 foot away will be blurry. The minimum distance can vary from about 2 feet to 12 feet, depending on the lens.
The majority of current cameraphones use fixed-focus lenses.